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TL25 User guide–- 33-60-021-000
1.13 NMEA link
The TL25 includes an NMEA input, allowing the connection of a GPS, a PC, meteorological
sensors, etc. After performing the NMEA initialisation of the TL25, the NMEA channels
corresponding to the frames transmitted by the instrument are available on the TOPLINE bus.
You can then display data.
Please note that if an instrument transmits an NMEA frame which is already created by an
nke
sensor, then this frame will not be taken into account.
1.13.1 Connection of the NMEA link
The NMEA input of the TL25 only allows the connection of one instrument providing NMEA
frames (see chapter 16). If you wish to connect a second instrument (for example a GPS and a
PC), you must connect it either to the NMEA input of another display, or to a TOPLINE NMEA
INPUT INTERFACE box (ref : 90-60-055).
1.13.2 NMEA initialisation procedure
−
Select the CONFIG channel on the upper display,
−
Press and hold the
key until the message «INIT NMEA» appears. Release the
key.
The TL25 subsequently performs a sequence of NMEA data search for 20 seconds, then it
creates the new channels corresponding to the NMEA frames transmitted by the instrument.
The NMEA channels created are saved in the display memory and restored every time it is
powered up.
1.13.3 Characteristics of NMEA data
The NMEA frames identified by the TL25 are in conformity with the NMEA standard 0183 V2.30
(or lower version).
The NMEA input is insulated by an optocoupler.
The format of the frames is : 4,800 bauds / 8 bits with bit 7 at 0 / 1 start bit and 1 stop bit.
Distances are truncated to the lower value.
The other dimensions are rounded to the nearest unit (ex : degrees for angles).
A frame can be partially empty between commas.
The TL25 will take the missing data in another frame (ex : speedometer in VWH and compass
in HDG).
The depth in feet will be identified if it does not exist in meters for example.
A channel can be included in several frames (ex : the compass is taken in HDG in priority, if not
in HDM, if not in VHW).
If the bottom heading or the WP heading do not exist in magnetic, the true heading is taken.
Refreshing of the display of the NMEA channels is performed each time a new valid NMEA
frame is received. If the NMEA link is lost (example : loss of satellites on the GPS) the last
received data will remain on the display for 64 seconds. After that, the TL25 will signal the
breakdown.
